

ABSTRACT

A down-hole motor is provided with stabilizer means 10A for centralizing the longitudinal motor axis I in a borehole and with a bearing unit 11 which supports the output shaft 5 in such an inclined position relative to the motor housing 1, that the central axis II of the output shaft 5 intersects the longitudinal axis I at a point of intersection 20 located outside the housing 1.Directional drilling of a borehole is carried out by actuating a drill bit 12 to rotate relative to the motor housing 1 about the central axis II of the output shaft 5 and simultaneously therewith rotating the motor housing 1 about the longitudinal motor axis I over periods that are preceded and succeeded by selected periods over which the motor housing 1 is not rotated.



